This invention relates, in general, to control devices and, more particularly, to a new and useful control device for an underground mining advancing support unit arrangement, for example, of hydraulic props and the like for underpinning a mine rod, in which a hydraulic working medium is supplied to several load points, having control valves, a combination of hydraulic control conduits and fittings associated with each support unit which connect or transmit the loads to the control valves, the control conduits being of the type having a normal diameter which permits direct control of the loads.
For safety reasons, the loads accommodated by the hydraulic working medium are controlled as a rule from a neighboring or adjacent support unit arrangement. The individual control valves are associated with a control block and are connected over control lines or conduits with the loads in the working support. Since each individual load point is connected through a feed and return line to the control valves, and since each support unit arrangement accommodates a plurality of load points, the space requirement for the hose lines is quite considerable and represents not only a great material consumption, but hinders at the same time the descent and increases the risk of damage by falling rocks or improper driving of the support unit arrangements. In this type of laying the the control lines it is advisable if the loads can be controlled directly from the control valves, because of the hose lines with a great nominal diameter.
In order to reduce the space required by the control lines laid between the support unit arrangement, it has been suggested (see West German Offenlegunschrift No. 27 00 829) to use control lines having small diameters which are connected to a multiple hose line. Multiple hose lines used in a so-called pilot control, characteristically, are additionally protected by sheathing the multiple hose. A disadvantage however, is that pilot valves are required, in addition to the main valves, which complicates the control and leads to higher material and maintenance costs. Pilot valves are necessary because direct control over multiple lines with a small cross section is not possible.
Based on the finding that the individual loads have a different consumption of working medium, it has been suggested (see West German Auslegesschrift No. 28 07 431) to indirectly actuate the load portions with a relatively great media consumption per unit of time, from the adjacent support unit, that is, over control hoses with a small cross section and pilot valves, and to directly actuate the load points, with a low media consumption per unit of time, from the main control valve in the adjacent support unit arrangement.
However, the great number of pilot valves required is still a disadvantage resulting in increased material and maintenance costs.